1. Field of the Invention
This invention generally relates to cells derived from adipose tissue, and more particularly, to adipose-derived regenerative cells (e.g., stem and/or progenitor cells), methods of using adipose-derived regenerative cells, compositions containing adipose-derived regenerative cells, and systems for preparing and using adipose-derived regenerative cells which are used to treat which are used to treat peripheral vascular disease and related conditions, diseases, or disorders.
2. Description of the Related Art
Peripheral vascular disease (PVD) and related disorders are defined as diseases of blood vessels outside of the heart and central nervous system often encountered as narrowing of the vessels of the limbs. There are two main types of these disorders, functional disease which doesn't involve defects in the blood vessels but rather arises from stimuli such as cold, stress, or smoking, and organic disease which arises from structural defects in the vasculature such as atherosclerotic lesions, local inflammation, or traumatic injury. This can lead to occlusion of the vessel, aberrant blood flow, and ultimately to tissue ischemia.
One of the more clinically significant forms of PVD is peripheral artery disease (PAD) which has elements in common with Coronary Artery Disease (CAD). Similarly to CAD, PAD is often treated by angioplasty and implantation of a stent or by artery by-pass surgery. Clinical presentation depends on the location of the occluded vessel. For example, narrowing of the artery that supplies blood to the intestine (i.e., the superior mesenteric artery) can result in severe postprandial pain in the lower abdomen resulting from the inability of the occluded vessel to meet the increased oxygen demand arising from digestive and absorptive processes. Severe forms the ischemia can lead to intestinal necrosis. Similarly, PAD in the leg can lead to intermittent pain, usually in the calf, that comes and goes with activity. This disorder is known as intermittent claudication (IC) and can progress to persistent pain while resting, ischemic ulceration, and even amputation. Currently available therapeutic interventions for PVD include thrombolytic drugs and anti-thrombotic drugs (heparin, aspirin, coumadin), exercise (for IC), anti-atherogenic drugs (e.g., statins), and surgical revascularization. However, many patients have a form of disease that is not anatomically suitable for surgical intervention.
Peripheral vascular disease is also manifested in atherosclerotic stenosis of the renal artery, which can lead to renal ischemia and kidney dysfunction. Biologic revascularization provides a potential alternative to surgical approaches. It involves the processes of angiogenesis and arteriogenesis which combine to drive development of new collateral blood flow techniques for by-passing blood flow around the occlusion. Biologic revascularization can be achieved by drug and gene therapy providing angiogenic factors or by cellular therapy delivering cells that contribute to angiogenesis by paracrine release of angiogenic factors and/or by providing a source of cells that can form endothelium.
Cellular therapy studies have been based on the detection of the presence of non-hematopoietic stem cells and endothelial precursor cells in bone marrow (Prockop, Azizi et al. 2000) (Pittenger, Mackay et al. 1999) (Shi, Rafii et al. 1998; Carmeliet and Luttun 2001). These studies used bone marrow transplant recipient animals in which donor and host cells could be distinguished by genetic markers to show that some fraction of new blood vessel development in the recipients was derived from the donor marrow cells (Carmeliet and Luttun 2001) (Takahashi, Kalka et al. 1999; Murayama, Tepper et al. 2002). While this work definitively demonstrates that marrow contains such cells mesenchymal stem cell frequency in bone marrow is estimated at between 1 in 100,000 and 1 in 1,000,000 nucleated cells (D'Ippolito et al., 1999; Banfi et al., 2001; Falla et al., 1993). Similarly, extraction of these cells from skin and other tissues involves a complicated series of cell culture steps over several weeks (Toma et al., 2001) and clinical application of skeletal muscle-derived stem cells requires a two to three week culture phase (Hagege et al., 2003). Thus, any proposed clinical application of stem cells from such tissues requires increasing cell number, purity, and maturity by processes of cell purification and cell culture.
Although cell culture steps may provide increased cell number, purity, and maturity, they do so at a cost. This cost can include one or more of the following technical difficulties: loss of cell function due to cell aging, loss of potentially useful non-stem cell populations, delays in potential application of cells to patients, increased monetary cost, and increased risk of contamination of cells with environmental microorganisms during culture. Recent studies examining the therapeutic effects of bone-marrow derived ASCs have used essentially whole marrow to circumvent the problems associated with cell culturing (Horwitz et al., 2001; Orlic et al., 2001; Stamm et al., 2003; Strauer et al., 2002). The clinical benefits, however, have been suboptimal, an outcome almost certainly related to the limited ASC dose and purity inherently available in bone marrow.
Recently, adipose tissue has been shown to be a source of stem cells (Zuk et al., 2001; Zuk et al., 2002). Adipose tissue (unlike marrow, skin, muscle, liver and brain) is comparably easy to harvest in relatively large amounts with low morbidity (Commons et al., 2001; Katz et al., 2001b). Suitable methods for harvesting adipose derived stem cells, however, are lacking in the art. The existing methods suffer from a number of shortcomings. For example, the existing methods may lack partial or full automation, a partial or completely closed system, disposability of components, etc.
Given the therapeutic potential of adipose derived stem cells for treating PVD, there exists a need in the art for a method for harvesting cells from adipose tissue that produces a population of adult stem cells with increased yield, consistency and/or purity and does so rapidly and reliably with a diminished or non-existent need for post-extraction manipulation.